In a display device such as a cathode ray tube display device (CRT), a plasma display (PDP), an electroluminescence display (ELD), or a liquid crystal display device (LCD), an anti-reflection film is generally arranged on the outermost surface of the display device to decrease the reflectance through the principle of optical interference to prevent a drop in the contrast owing to the reflection of external light or prevent reflection of undesired images in its screen.
Such an anti-reflection film can be produced by forming a high-refractive-index layer on a support and further forming a low-refractive-index layer having an appropriate thickness thereon. In this case, it is preferred from the standpoint of productivity that the respective layers can be formed by wet coating.
To realize low reflectance, the low-refractive-index layer is desirably made of a material whose refractive index is as low as possible. High scratch resistance is required for the anti-reflection film, since it is used as the outermost surface of a display. To lower the refractive index of the material, it is possible to adopt the method (1) of introducing a fluorine atom into the material, or the method (2) of lowering the density of the material (introducing voids into the material). However, with both of the methods, a tendency was generated for mechanical strength of the coating to be damaged and the scratch (abrasion) resistance to deteriorate. Thus, it was difficult to achieve both a low refractive index and high scratch resistance at the same time.
Various methods are known for curing a fluorine-containing polymer having a low refractive index. As described in, for example, JP-A-57-34107 (“JP-A” means unexamined published Japanese patent application), JP-A-61-258852, JP-A-61-275311, JP-A-62-185740, JP-A-62-292848, JP-A-8-92323, and JP-A-12-17028, generally, a polymer having a hydroxyl group or the like was cured by various hardeners. However, hardeners and fluorine-containing polymer had problems in mutual solubility (miscibility) in many cases. Therefore, improvements in the transparency of the resultant polymer, and the hardness of the coating, has been desired. Against the problems, JP-A-10-25388 disclosed a technique in which a melamine-series hardener and a hydroxyl group-containing low-refractive-index polymer, were heated beforehand, so as to be partially condensed. The technique was advantageous for making the transparency of the coating high to a certain extent, but it is difficult to say this effect was sufficient.